Valves can be used to control the flow of material through an orifice. Certain valves, such as ball and seat valves and tip seal valves, include an arrangement whereby a shaft or stem includes a particularly-shaped tip, which is mated with a seat. One common shape for the tip is a substantially round ball, though other shapes are known as well. The valve is shut “off” when the tip is engaged with the seat and the valve is “on” when the tip is removed from the seat. The stem is typically connected to a piston or actuator that facilitates the movement of the tip relative to the seat. The tip and stem assembly typically moves linearly relative to the seat, thereby controlling the flow of material through the orifice in the seat. As discussed hereinafter, this type of valve will be identified generically as a “ball and seat” valve, though, as indicated above, the tip may have other shapes besides a “ball.”
Such valve systems have many applications. For example, a ball and seat valve can be used as a one-way check valve that limits material flow through the orifice to one direction. Further, it can be used to selectively adjust (limit) the amount of flow through a system. An automatic or manual ball and seat valve can also be used in dispensing and metering systems. Dispensing and metering systems are generally used to provide a measured amount of material for a particular application. Dispensing and metering systems ensure that a specified amount of material is delivered each time the material is required. For example, manufacturing an automobile often requires numerous applications of precisely metered materials, such as the application of sealants to an automobile's body structure. Dispensing and metering devices can eliminate the guesswork, human error, and waste associated with trying to apply a precise amount of material by hand.
In certain applications, a valve can be subjected to harsh conditions that can potentially damage one or more components of the valve assembly. For example, such valve assemblies can be subjected to high pressure, corrosive materials, and strong forces from the flowing material. Such harsh conditions can potentially cause a tip to separate from its stem. Thus, the particular construction of the tip and stem assembly can be of significant importance. In applications subjecting the tip and stem assembly to such harsh conditions, the particular manner of bonding and/or press fitting a tip to a stem can greatly reduce the possibility of valve damage.
A tip and stem assembly can be constructed in many ways. For example, a tip and stem assembly can be made by rounding one end of a solid elongated cylindrical rod. However, the various manufacturing processes that can be used to round one end of a rod could lead to imperfections in the tip. Imperfections in the tip can cause mating problems between the tip and seat, and thereby lead to a leaky valve. A tip and stem assembly could also be made by welding a solid sphere to an end of a rod. However, such an assembly would have very limited bonding surface area between the sphere and the rod, possibly resulting in a tip and stem assembly that is more apt to separate under harsh conditions. Thus, to greatly reduce the possibility of damage to a tip and stem assembly subjected to harsh conditions, the tip and stem assembly should be constructed such that the tip is substantially free from deformities and securely bonded to a stem over a significant surface area.